Cathode ray tube



Nov. 22, 1938. K. SCHLESINGER 2,137,352

CATZHODE RAY TUBE Filed Jan. 7, 1955 9n ven Far:

Patented Nov. 22, 193$ UNlTED srarss OATHODE RAY TUBE Kurt Schlesinger,Berlin, Germany, assignor to Radioaktiengesellschaft D.

Steglitz, Germany S. Loewe, Berlin- Application January '7, 1935, SerialNo. 725

In Germany January 12, 1934.

22 Claims.

Braun tubes have already been described by the applicant in earlierapplications, in which an emissive surface (i. e., the cathode, adiaphragm or a suitable intermediate surface) is reproduced sharply onthe image screen by the use of an electron-optical system.

Further, means have already been described by the applicant for lightinga diaphragm of this nature with a bundle of electrons which is asparallel as possible.

The electron-optical systems employed in this connection consistfundamentally of an electrode linked up with a potential which is low byway of comparison, and an after-connected electrode having a highpositive potential. Since the system employed for lighting the apertureof the diaphragm is also constructed on similar lines, it has been foundthat the electrode situated next to the cathode can possess merely aweak positive potential.

An increase in the potential of this first suctional electrode, by thesuctional action of which there is determined in practice the maximumemission of the cathode, appeared impossible without either destructionof the electron-optical structure, making a sharp reproductionimpossible, or employing extremely high potentials at -the last anode ofthe system.

In consequence it has not been possible in these tubes to obtain acathode ray of great intensity, and accordingly image points of highluminosity.

The subject matter of the invention is an additional development ofthese arrangements, which avoids the disadvantages referred to andenables sharp image points of very high intensity of light to beproduced by the use of the relatively low anode potentials usualheretofore (of the order of 1000-2000 volts).

According to the invention, the diaphragm to be reproduced-for exampleby connection with the high-potential anode-is raised to a potential ashigh as possible, and. the after-connected first electrode of theelectron-optical system, which requires a positive potential that is lowby Way 4'5 of comparison, is constructed in such fashion that thepotential planes following the diaphragm remain substantiallyplano-parallel despite the great jump in potential between the diaphragmand the after-connected element.

50 This may be accomplished in accordance with the invention by the factthat the after-connected electrode is constructed in the form of a tube,the diameter of which is very large in, comparison with the aperture inthe diaphragm.

55 If a special system is not. employed for lighting the diaphragm, thehigh potential thereof takes full effect as suctional potential. In thiscase, however, it is necessary to make the distance between the cathodeand the diaphragm comparatively largefor example 10% of the length of 5the tube following the diaphragm, i. e., with a length of tube amountingto 30 mm. approximately 3 mm., as otherwise in addition to the diaphragmthere is also reproduced simultaneously the surface of the cathodeitself, and in this 10 manner a large blurred image point formed havingan edge.

If on the other hand a special system is employed for lighting thediaphragm, the element of this system connected in front of thediaphragm-as the latter is raised to a very high positive potential-*mayalways possess a comparatively high positive potential, which iscompletely adequate for the generation of an intense cathode ray. 20

In this case it is also possible to place the first element much nearerto the cathode-for example, to within /2 mm.

Certain forms of embodiment of the arrangement according to theinvention are illustrated 25 by way of example in the drawing, in whichFig. 1 is an arrangement without preliminary concentration, whilst inFig. 2 there is shown an arrangement with preliminary concentration, andin 30 Fig. 3 an arrangement with consideration to the deflecting plates,in which arrangement a potential distributing means may be arranged atthe same time in the vacuum of the tube.

In the drawing: 35

I is the indirectly heated cathode having an oxide surface of exactlydefined form, which is preferably let in and is heated by a filament 3.The aperture in the diaphragm d is lighted by the bundle of electronsproceeding from the oxide 40 surface. Behind the diaphragm l there isarranged the electron-optical system, which reproduces the aperture ofthe diaphragm on the image screen. The electron-optical system consistsaccording to the invention of an electrostatic lens with large aperture,which is formed by two cylinders 6 and l, of which the front onepossesses a higher positive potential than the cylinder '6. According tothe invention, both cylinders are provided with a diameter which is verylarge in relation to the aperture in the diaphragm. In this manner it isaccomplished that the electron-optical effect of the system remainssubstantially unaffected by the series-connected electrode of highpotential (there is avoided the formation of a lens surface at thebounding plane between the electrode 3 and the cylinder 6) As alreadyset forth, the distance between the cathode surface 2 and the diaphragmaperture requires to be comparatively large-for example, approximately 3mm.

An additional form of embodiment of the arrangement according to theinvention is illustrated in Fig. 2.

This relates to a tube for television purposes, which reveals in face'of Fig. l the peculiarity that the strength of the emission current maybe varied by means of a control grid 8 in front of the surface of thecathode. In order upon this operation to ensure that the form of theimage point will be properly constant an auxiliary condenser lenscomprising the two cylinder electrodes 9 and 4 has been found to beessential in tubes of this kind, in which connection the potential ofthe preliminary anode 9 requires. to. be less positive than thepotential of the diaphragm 4, and in which, therefore, in the knownarrangements, even a smaller suctional potential has been available infront of the cathode surface than in the tube according to Fig. 1. Theorders of magnitude in practice are, for example:

7 Volts Main anode potential (7) 2000 Potential of the tube (6) 300Potential of the preliminary anode (9) ap prox 50 There accordinglyarises in the known arrangements with electrostatic acceleration lensesthe diiiiculty of obtaining large current maxima from the cathodes, asthe anode potentials available in front of the cathode are merelyfractions of the total anode potential of the tube, and as they are of afixed nature by reason of the electronoptical conditions of the focusand cannot be altered.

The basic idea of the invention consists in biasing the diaphragm 4,which represents the electron-optical object as regards the image pointon the screen, to a particularly high positive potential, which ishigher than the potential of the tube 6, i. e., the following lenselement. This method is only capable of being performed if the potentialplanes linking up with the diaphragm l remain piano-parallel. Thereotherwise occurs, in addition to the unavoidable braking effect to whichthe electrons are subjected in the tube space 5 after leaving thediaphragm, an undesirable auxiliary refractive effect in the directionof concentration, which would result in an increase in the scale ofreproduction, and accordingly in a thickening of the image point on thescreen. According to the invention, therefore, the diameter of the tube6 is made practically infinitely large as compared with the diameter ofthe aperture in the diaphragm or the medium cross-section of the ray inthe vicinity of the diaphragm, and the diaphragm plate 4 is made flat.it may then be proved from a potentialtheoretical point of view, andalso confirmed by experiment, that it is possible to introduce betweenthe diaphragm i and the tube 6 differences in potential amounting toseveral times 100-1000 volts without the sharpness or the adjustment ofthe focus of the main electrostatic lens 6, 7 thus being changed. Inaccordance with the invention the diaphragm 4 in Figs. 1 and 2 mayaccordingly be connected, for example, as shown, with the main anode 1.Since with a constant scale of reproduction on the part of the condenserens 2, 9, 4 the ratio of the potential between the stated electrodesalso remains the same, the 150* tential at the anode 9, in accordancewith the invention, may also be increased in proportion with thepotential of 4. In the stated example, therefore, a suctional anodepotential of approximately 300 volts is obtained. It has been measuredin practice that with a maximum emission of, for example, 100 A., withthe stated potentials and the connection of 4 and 6, an increase couldbe made up to a strength of emission current amounting to 550 A. afteruse of the separate biasing in accordance with the invention of thediaphragm 3 and the tube 6. The yield of current, i. e., the ratiobetween that measured at the screen 5 and the strength of emissioncurrent in the cathode line No, is equally good in both cases (over 80%)An additional important advantage of the stated bias between diaphragm 4and tube 6 the equipotential observation shows that the usual secondarylight at the screen 5, for example in the case of a tube according toFig. l, disappears entirely even with small biases between 4 and 6.Tubes without a condenser according to Fig. 1 practically always reveala strong general lighting of the luminous screen 5 also outside of theactual electronic image point. This lighting, as the applicant hasfound, is due primarily to marginal rays which are not to be avoidedwith the simple form of diaphragm lighting and owing to a sphericalerror in the main lens 6,] do not reach the point of reproduction (theyare too greatly deflected). By reason of the bias according to theinvention there is an appreciable concentrating effect in the space ofthe tube 6 in respect of marginal rays deviating to this extent, as inthe tube the radial field densities, so far as the same are present atall, are directed at all points inwardly. t

In making use of this efiect, which is to be observed in practice, ithas been found that the exact extent of the bias between 4 and 6 is notof utmost importance from the point of view of overcoming the haloeffect. It is possible,- therefore, in accordance with the invention, bythe provision of potential distributing resistances in the interior ofthe tube system, to produce a suitable bias, and at the same time tomake do with merely one variable focal potential altogether outside ofthe tube.

Fig. 3 shows the diaphragm electrode 4 in conjunction with an outerterminal 4', which may be adjusted by hand in connection with apotential distributor. The two resistances l0 and l I are prow'dedwithinthe tube, and amount for example to l and 2 megohms respectively,so that they do not represent an appreciable load on the anode battery.Whilst, therefore, the suction anode potential is adjusted at 4',regulation is performed simultaneously to the correct focal distanceowing to the difference in potential 6-1, and there is obtained thedesired positive bias of the diaphragm 4 in relation to the tube 5according to the invention, and accordingly a sufficiently powerfulemission of electrons from the cathode I-2. The oxide surface maypossess in practice a diameter of approximately .5 mm., and thediaphragm aperture of 4 diameter of .3 mm.

Finally, it may be remarked that the tubular form of the main anode withrelatively long tubular abutment (approximately 15 mm.) shownvthroughout in the drawing represents merely a particular instance ofother possible constructions of anode and lens. The same, however,ofiers the advantage of also possessing at the point where the cathoderay reveals its greatest diameter the largest aperture. It is possible,therefore, according to the invention, to furnish the tubular memberwith a relatively small outlet aperture, as the rays have beenappreciably bundled together within the tubular anode. In this mannerinterference of the deflecting plates l2-l3, which are arranged behindthe anode l, in the lens field will be avoided to a large extent, andgood sharpness of the image point ensured up to the edge of the luminousimage.

The arrangement according to Fig. 1 is particularly suitable foroscillographic purposes.

Also in the arrangement in which the diaphragm is lighted by the use ofa special device having a bundle of electrons made parallel (asdescribed in the above, the device is preferably so constructed that anintersection of the electronic rays is avoided in the place of thediaphragm) it may be desirable to arrange this device at a comparativelylarge distance (for example 2i-3 mm) from the surface of the cathode.

The arrangement or arrangements to the invention, with correspondingmodification in the form of electrode (use of box or plate electrodes inplace of the cylinder as described), may be used for amplifier tubesaccording to the transverse field principle.

I claim:

1. In a television arrangement a cathode ray tube comprising an electronbeam producing system including a cathode, voltage supplying meansassociated with said system for causing said system to produce anelectron beam, an image screen in said cathode ray tube; means forelectronoptically reproducing a cross-sectional portion of said electronbeam onto said image screen, said last mentioned means comprisingelectrodes 'mounted inside said cathode ray tube in the space betweensaid cathode and said image screen to form an electron optical system,the first one of said electrodes taken from said cathode having theshape of a hollow cylinder of the diameter d, with its axis directedfrom said cathode to said image screen, and means for applying diiierentpotentials to said electrodes, the potential applied to said firstelectrode taken from the cathode being in the order of 300 volts inrelation to said cathode; a plate shaped electrode having an aperture ofa diameter in the order of to V of d mounted in the space between saidelectronoptical system and said cathode in close vicinity of said firstelectrode of said electron-optical system; and means for applying tosaid plate shaped electrode a high positive potential in relation tosaid first electrode of said electron optical system.

2. In a television arrangement a cathode ray tube having a cathode, ananode, and an image screen, means for producing an electron beam in saidcathode ray tube, said means comprising said cathode, said anode, andmeans for applying to said anode a high positive potential in relationto said cathode; means for electron-optically reproducing across-sectional portion of said electron beam onto said image screen,said last mentioned means comprising said anode and an electrode havingthe shape of a hollow cylinder of the diameter d, mounted in the spacebetween said cathode and said anode with its axis directed from saidcathode to said anode to form together with said anode anelectron-optical system, and means for applying to said electrodes apotential considerably difierent from that applied to said anode; aplate shaped electrode having an aperture of a diameter in the order ofto of d mounted in the space between said electronoptical system andsaid cathode in close vicinity of said first electrode of saidelectron-optical system; and means for directly connecting said plateshaped electrode with said anode.

3. In a television arrangement a cathode ray tube comprising an electronbeam producing system including a cathode, voltage supplying meansassociated with said system for causing said system to produce anelectron beam, an image screen in said cathode ray tube; means forelectron-optically reproducing a cross-sectional portion of saidelectron beam onto said image screen, said last mentioned meanscomprising electrodes mounted inside said cathode ray tube in the spacebetween said cathode and said image screen to form an electron-opticalsystem, the first one of said electrodes taken from said cathode havingthe shape of a hollow cylinder of the diameter d, with its axis directedfrom said cathode to said image screen, the second one of saidelectrodes taken from the cathode having the shape of a hollow cylinderof the same mentioned diameter d and a length of the order of 2 to 3centimetres, the axis of said second mentioned cylinder coinciding withthat of said first mentioned cylinder, means for applying to said firstmentioned cylinder a potential of the order of 300 volts in relation tosaid cathode, means for applying to said second mentioned cylinder apotential of the order of 1500 to 2000 volts in relation to saidcathode; a plate shaped electrode having an aperture of a diameter inthe order of A to of d mounted in the space between saidelectron-optical system and said cathode in close vicinity of said firstelectrode of said electron-optical system; and means for applying tosaid plate shaped electrode a high positive potential in relation tosaid first electrode of said electron optical system.

4. In a television arrangement a cathode ray tube comprising an electronbeam producing system including a cathode, voltage supplying meansassociated with said system for causing said system to produce anelectron beam, an image screen in said cathode ray tube; means forelectron-optically reproducing a crosssectional portion of said electronbeam onto said image screen, said last mentioned means comprisingelectrodes mounted inside said cathode ray tube in the space betweensaid cathode and said image screen to form an electron optical system,the first one of said electrodes taken from said cathode having theshape of a hollow cylinder of the diameter d, with its axis directedfrom said cathode to said image screen, the second one of saidelectrodes taken from the cathode having the shape of a hollow cylinderof the same mentioned diameter d and a length of the order of 2 to 3centimetres, the axis of said second men tioned cylinder coinciding withthat of said first mentioned cylinder, a plate with an aperture of adiameter considerably smaller than 01 closing ofi said second mentionedcylinder on that side directed towards said image screen, means forapplying to said first mentioned cylinder a potential of the order of300 volts in relation to said cathode, means for applying to said secondmentioned cylinder a potential of the order of 1500 to 2000 volts inrelation to said cathode; a plate shaped electrode having an aperture ofa diameter in the order of to & of d mounted in the space between saidelectron-optical system and said cathode in close vicinity of said firstelectrode of said electron-optical system; and means for applying tosaid plate shaped electrode a high positive potential in relation tosaid first electrode of said electron-optical system.

5. In a television arrangement a cathode ray tube comprising an electronbeam producing system including a cathode, voltage supplying meansassociated with said system for causing said system to produce anelectron beam, an image screen in said cathode ray tube; means forproducing an electron optical reproduction of a cross-sectional portionof said electron beam on said screen; at least one pair of deflectingplates for causing said reproduction to scan at least a part of saidimage screen; said means for producing an electron-optical reproductionof said electron emissive surface comprising electrodes mounted insidesaid cathode ray tube in the space between said cathode and said imagescreen to form an electron optical system, the first one of saidelectrodes taken from said cathode having the shape of a hollow cylinderof the diameter d, with its axis directed from said cathode to saidimage screen, the second one of said electrodes taken from the cathodehaving the shape of a hollow cylinder of the same mentioned diameter dand a length of the order of 2 to 3 centimetres, the axis of said secondmentioned cylinder coinciding with that of said first-mentionedcylinder, a plate with an aperture of a diameter smaller than thedistance between the plates of said pair closingoff said secondmentioned cylinder on that side directed towards said image screen,means for applying to said first mentioned cylinder a potential of theorder of 300 volts in relation to said cathode, means for applying tosaid second mentioned cylinder a potential of the order of 1500 to 2000volts in relation to said cathode; a plate shaped electrode having anaperture of a diameter in the order of to of (I mounted in the spacebetween said electronoptical system and said cathode in close vicinityof said first electrode of said electron-optical system; and means forapplying to said plate shaped electrode a high positive potential inrelation to said first electrode of said electron-optical system.

6. In a television arrangement a cathode ray tube comprising an electronbeam producing system including a cathode, voltage supplying meansassociated with said system for causing said system to produce anelectron beam, an image screen in said cathode ray tube; means forelectron-optically reproducing a cross-sectional portion of saidelectron beam onto said image screen,

said last mentioned means comprising electrodes mounted inside saidcathode ray tube in the space between said cathode and said image screento form an electron optical system, the first one of said electrodestaken from said cathode having the shape of a hollow cylinder of thediameter d, with its axis directed from said cathode to said imagescreen, and means for applying different potentials to said electrodes;a plate shaped electrode having an aperture, the diameter of which is inthe order of to of d, mounted in the space between said electron-opticalsystem and said cathode in close vicinity of said first electrode ofsaid electron-optical system; and means for applying a high potentialdifference between said first electrode of said electronoptical systemand said plate-shaped electrode.

7. In a television arrangement a cathode ray tube, comprising anelectron beam producing system including a cathode, voltage supplyingmeans associated with said system for causing said system to produce anelectron beam, an image screen in said cathode ray tube; means forelectronoptically reproducing a cross-sectional portion of said electronbeam onto said image screen, said last mentioned means mounted insidesaid cathode ray tube in the space between said cathode and said imagescreen to form an electron optical system, the first one of saidelectrodes taken from said cathode having the shape of a hollow cylinderof the diameter d, with its axis directed from said cathode to saidimage screen, and means for applying different potentials to saidelectrodes; a plate shaped electrode having an aperture, the diameter ofwhich is in the order of one-thirtieth to one-twentieth of d, mounted inthe space between said electronoptical system and said cathode in closevicinity of said first electrode of said electron-optical system and ina distance of the order of 3 to 5 millimetres from the cathode to avoida reproduction of the cathode surface onto said image screen.

8. In a television arrangement a cathode ray tube comprising an electronbeam producing system including a cathode, voltage supplying meansassociated with said system for causing said syscomprising electrodestem to produce an electron beam, an image screen in said cathode raytube; means for electronoptically reproducing a cross-sectional portionof said electron beam onto said image screen, said last mentioned meanscomprising electrodes mounted inside said cathode ray tube in the spacebetween said cathode and said image screen to form an electron opticalsystem, the first one of said electrodes taken from said cathode havingthe shape of a hollow cylinder of the diameter d, with its axis directedfrom said cathode to said image screen, and means for applying differentpotentials to said electrodes; a plate shaped electrode having anaperture, the diameter of which is in the order of to /20 of d, mountedin the space between said electron-optical system and said cathode inclose vicinity of said'first electrode of said electron-optical system;and means for applying to said plate-shaped electrode a high positivepotential in relation to said first electrode of said electron-opticalsystem.

9. In a television arrangement a cathode ray tube comprising an electronbeam producing system including a cathode, voltage supplying meansassociated with said system for causing said system to produce anelectron beam, an image screen in said cathode ray tube; means forproducing in a part of the space enclosed by said tube between saidcathode and said screen an electron lens field for reproducing across-sectional portion of said electron beam onto said image screen, atubular electrode having a diameter 02 mounted between said cathode andsaid image screen with its axis directed from said cathode to said imagescreen, said tubular electrode extending, in the direction from saidcathode to said image screen, at most up to the part of the spaceenclosed by said tube in which, as hereinbefore set forth, the electronlens field is formed, a plate-shaped electrode having an aperture, thediameter of which is in the order of to & of (I, mounted in the spacebetween said tubular electrode and said cathode in close vicinity ofsaid tubular electrode, and means for applying a high potentialdifierence between said tubular electrode and said plate-shapedelectrode.

10. In a television arrangement a cathode ray tube having a cathode, ananode, and an image screen, means for producing an electron beam in saidcathode ray tube, said means comprising said cathode, said anode, andmeans for applying to said-anodea high positive potential in relation tosaid cathode, means for electron-optically reproducing a cross-sectionalportion of said electron beam onto said image screen, said lastmentioned means comprising said anode and an electrode having the shapeof a hollow cylinder of the diameter d, mounted in the space betweensaid cathode and said anode with its axis directed from said cathode tosaid anode to form together with said anode an electron-optical system,and means for applying to said electrodes a potential consider ablydifferent from that applied to said anode; a plate-shaped electrodehaving an aperture of a diameter in the order of ,6, to of d mounted inthe space between said electron-optical system and said cathode in closevicinity of said first electrode of said electron-optical system; andmeans for applying to said plate-shaped electrode a potential which isconsiderably difierent from that applied to said first electrode of saidelectronoptical system.

11. In a television arrangement a cathode ray tube having a cathode, ananode, and an image scr en, means for producing an electron beam in saidcathode ray tube, said means comprising said cathode, said anode, andmeans for applying to said anode a high positive potential in relationto said cathode; means for electron-optically reproducing across-sectional portion of said electron beam onto said image screen,said last i'mentioned means comprising said anode and. an electrodehaving the shape of a hollow cylinder of the diameter d, mounted in thespace between said cathode and said anode with its axis directed fromsaid cathode to said anode to form together with said anode anelectron-optical system, and means for applying to said electrode apotential considerably lower than that applied to said anode; aplate-shaped electrode having an aperture of a diameter in the order ofto of d mounted in the space between said electronopti-cal system andsaid cathode in close vicinity of said first electrode of saidelectron-optical system; and means for directly connecting saidplate-shaped electrode with said anode.

12. In a television arrangement a cathode ray tube comprising anelectron beam producing system including a cathode, voltage supplyingmeans associated with said system for causing said system to produce anelectron beam, an image screen in said cathode ray tube; means forelectron-optically reproducing a cross-sectional portion of saidelectron beam onto said image screen, said last mentioned meanscomprising electrodes mounted inside said cathode ray tube in the spacebetween said cathode and said image screen to form an electron-opticalsystem, the first one of said electrodes taken from said cathode havingthe shape of a hollow cylinder of the diameter d, with its axis directedfrom said cathode to said image screen, and means for applying differentpotentials to said electrodes, the potential applied to said firstelectrode taken from the cathode being in the order of 300 voltspositive in relation to said cathode; a plate shaped electrode having anaperture of a diameter in the order of /o to 1 of d mounted in the spacebetween said electron-optical system and said cathode in close vicinityof said first electrode of said electron-optical system; and means forapplying to said plate-shaped electrode a high positive potential inrelation to said first electrode of said electron optical system.

13. In a television arrangement a cathode ray tube having'a cathode, ananode, and an image screen, means for producing an electron beam in saidcathode ray tube, said means comprising said cathode, said anode, andmeans for supplying to said anode a high positive potential in relationto said cathode; means for electronoptically reproducing across-sectional portion of said electron beam onto said image screen,said last mentioned means comprising said anode and an electrode havingthe shape of a hollow cylinder of the diameter d, mounted in the spacebetween said cathode and said anode with its axis directed from saidcathode to said anode to form together with said anode an electronoptical system and means for applying to said electrode a potentialpositive relatively to said cathode and considerably different from thatapplied to said anode; a plate-shaped electrode having an aperture of adiameter in the order of to & of d mounted in the space between saidelectronoptical system and said cathode in close vicinity of said firstelectrode of said electron-optical system; and means for directlyconnecting said plate-shaped electrode with said anode.

14. In a television arrangement a cathode ray tube comprising anelectron beam producing system including a cathode, voltage supplyingmeans associated with said system for causing said system to produce anelectron beam, an image screen in said cathode ray tube; means forelectron-optically reproducing a cross-sectional portion of saidelectron beam onto said image screen, said last mentioned meanscomprising electrodes mounted inside said cathode ray tube in the spacebetween said cathodeand said image screen to form an electron-opticalsystem, the first one of said electrodes taken from said cathode havingthe shape of a hollow cylinder of the diameter d, with its axis directedfrom said cathode to said image screen, the second one of saidelectrodes taken from the cathode having the shape of a hollow cylinderof the same mentioned diameter and a length of the order of 2 to 3centimeters, the axis of said second mentioned cylinder coinciding withthat first mentioned cylinder, means for applying to said firstmentioned cylinder a potential of the order of 300 volts positive inrelation to said cathode, means for applying to said second mentionedcylinder a potential of the order of 1500 to 2000 volts positive inrelation to said cathode; a plateshaped electrode having an aperture ofa diameter in the order of A to of d mounted in the space between saidelectron-optical system and said cathode in close vicinity of said firstelectrode of said electron-optical system; and means for applying tosaid plate-shaped electrode a high positive potential in relation tosaid first electrode of said electron-optical system.

15. In a television arrangement a cathode ray tube comprising anelectron beam producing system including a cathode, voltage supplyingmeans associated with said system for causing said system to produce anelectron beam, an image screen in said cathode ray tube; means forelectron-optically reproducing a cross-sectional portion of saidelectron beam onto said image screen, said last mentioned meanscomprising electrodes mounted inside said cathode ray tube in the spacebetween said cathode and said image screen to form an electron-opticalsystem, the first one of said electrodes taken from said cathode havingthe shape of a hollow cylinder of the diameter d, with its axis directedfrom said cathode to said image screen, the

second one of said electrodes taken from the cathode having the shape ofa hollow cylinder of the same mentioned diameter d and a length of theorder of 2 to 3 centimetres, the axis of said second mentioned cylindercoinciding with that of said first mentioned cylinder, a plate with .anaperture of a diameter considerably smaller than (2 closing off saidsecond mentioned cylinder on that side directed towards said imagescreen, means for applying to said first mentioned cylinder a potentialof the order of 300 volts positive in relation to said cathode, meansfor applying to said second mentioned cylinder a potential of the orderof 1500 to 2000 volts positive in relation to said cathode; aplate-shaped electrode having an aperture of a diameter in the order of1 to of d mounted in the space between said electronoptical system andsaid cathode in close vicinity of said first electrode of saidelectron-optical system; and means for applying to said plateshapedelectrode a high positive potential in relation to said first electrodeof said electronoptical system.

16. In a television arrangement a cathode ray tube comprising anelectron-beam producing system including voltage supplying meansassociated with said system for causing said system to produce anelectron beam, an image screen in said cathode ray tube; means forproducing an electron-optical reproduction of a cross-sectional portionof said electron beam on said screen; at least one pair of deflectingplates for causing said reproduction to scan at least a part of saidimage screen; said means for producing an electron-optical reproductionof said electron emissive surface comprising electrodes mounted insidesaid cathode ray tube in the space between said cathode and said imagescreen to form an electron-optical system, the first one of saidelectrodes taken from said cathode having the shape of a hollow cylinderof the diameter d, with its axis directed from said cathode to saidimage screen, the second one of said electrodes taken from the cathodehaving the shape of a hollow cylinder of the same mentioned diameter dand a length of the order of 2 to 3 centimetres, the axis of said secondmentioned cylinder coinciding with that of said first mentionedcylinder, a plate with an aperture of a diameter smaller than thedistance between the plates of said pair closingofi" said secondmentioned cylinder on that side directed towards said image screen,means for applying to said first mentioned cylinder a potential of theorder of 300 volts positive in relation to said cathode, means forapplying to said second mentioned cylinder a potential of the order of1500 to 2000 volts positive in relation to said cathode; a plate-shapedelectrode having an aperture of a diameter in the order of to of dmounted in the space between said electron-optical system and saidcathode in close vicinity of said first electrode of saidelectronoptical system; and means for applying to said plate-shapedelectrode a high positive potential in relation to said first electrodeof said electronoptical system.

17. In a television arrangement a cathode ray tube comprising anelectron beam producing system including a cathode, voltage supplyingmeans associated with said system for causingsaid system to produce anelectron beam, an image screen in said cathode ray tube; means-forelectron-optically reproducing a cross-sectional portion of saidelectron beam onto said image screen, said last mentioned meanscomprising electrodes mounted inside said cathode ray tube in the spacebetween said cathode and said image screen to form an electron-opticalsystem, the first one of said electrodes taken from said cathode havingthe shape of a hollow cylinder of the diameter d, with its axis directedfrom said cathode to said image screen, and means for applying difierentpotentials to said electrodes; a plateshaped electrode having anaperture, the diameter of which'is in the order of to $5 of d, mountedin the space between said electron-optical system and said cathode inclose vicinity of said first electrode of said electron-optical system;means for maintaining said first electrode of said electron-opticalsystem positive relatively to said cathode, and means for applying ahigh potential diflerence between said first electrode of saidelectron-optical system and said plate-shaped electrode.

18. In a television arrangement a cathode ray tube comprising anelectron beam producing system including a cathode, voltage supplyingmeans associated with said system for causing said system to produce anelectron beam, an image screen in said cathode ray tube; means forelectronoptically reproducing a cross-sectional portion of said electronbeam onto said image screen, said last mentioned means comprisingelectrodes mounted inside said cathode ray tube tube in the spacebetween said cathode and said image screen to form an electron-opticalsystem, the first one of said electrodes taken from said cathode havingthe shape of a hollow cylinder of the diameter d, with its axis directedfrom said cathode to said image screen, and means for applying differentpotentials to said electrodes of which the potential applied to saidfirst electrode of said electron-optical system is positive relativelyto said cathode; a plate-shaped electrode having an aperture, thediameter of which is in the order of 1 to of d, mounted in the spacebetween said electron-optical system and said cathode in close vicinityof said first electrode of said electron-optical system and at adistance of the order of 3 to 5 millimetres from the cathode to avoid areproduction of the cathode surface onto said image screen.

19. In a television arrangement a cathode ray tube comprising anelectron beam producing system including a cathode, voltage supplyingmeans associated with said system for causing said system to produce anelectron beam, an image screen in said cathode ray tube, means forelectron-optically reproducing a cross-sectional portion of saidelectron beam onto said image screen, said last mentioned meanscomprising electrodes mounted inside said cathode ray tube in the spacebetween said cathode and said image screen to form an electron-opticalsystem, the first one of said electrodes taken from said cathode havingthe shape of a hollow cylinder of the diameter 07, with its axisdirected from said cathode to said image screen, and means for applyingdifierent 20. In a television arrangement a cathode ray tube comprisingan electron beam producing system including a cathode, voltage supplyingmeans associated with said system for causing said system to produce anelectron beam, an image screen in said cathode ray tube, means forproducing in a part of the space enclosed by said tube between saidcathode and said screen an electron lens field for reproducing across-sectional portion of said electron beam onto said image screen, atubular electrode having a diameter d mounted between said cathode andsaid image screen with its axis directed from said cathode to said imagescreen, said tubular electrode extending, in the direction from saidcathode to said image screen, at most up to the part of the spaceenclosed by said tube in which, as hereinbefore set forth, theelectron-lens field is formed, a plate-shaped electrode having anaperture, the diameter of which is in the order of to of d, mounted inthe space between said tubular electrode and said cathode in closevicinity of said tubular electrode, means for maintaining said tubularelectrode positive relatively to said cathode, and means for applying ahigh potential difference between said tubular electrode and saidplate-shaped electrode.

21. In a television arrangement a cathode ray tube having a cathode, ananode, and an image screen, means for producing an electron beam in saidcathode ray tube, said means comprising said cathode, said anode, andmeans for applying to said anode a high positive potential in relationto said cathode, means for electron-optically reproducing across-sectional portion of said electron beam onto said image screen,said lastmentioned means comprising said anode and an electrode havingthe shape of a hollow cylinder of the diameter d, mounted in the spacebetween said cathode and said anode with its axis directed from saidcathode to said anode to form together with said anode anelectron-optical system, and means for applying to said electrode apotential positive relatively to said cathode and considerably differentfrom that applied to said anode; a plate-shaped electrode having anaperture of a diameter in the order of to 3 of d mounted in the spacebetween said electron-optical system and said cathode in close vicinityof said hollow cylinder-shaped electrode; and means for applying to saidplate-shaped electrode a potential which is considerably different fromthat applied to said hollow cylinder-shaped electrode.

22. In a television arrangement a cathode ray tube having a cathode, ananode, and an image screen, means for producing an electron beam in saidcathode ray tube, said means comprising said cathode, said anode, andmeans for applying to said anode a high positive potential in relationto said cathode; means for electron-optically reproducing across-section portion of said electron beam onto said image screen; saidlast mentioned means comprising said anode and an electrode having theshape of a hollow cylinder of the diameter (I, mounted in the spacebetween said cathode and said anode with its axis directed from saidcathode to said anode to form together with said anode anelectron-optical system, and means for applying to said electrode apotential positive relatively to said cathode and considerably lowerthan that applied to said anode; a plate-shaped electrode having anaperture of a diameter in the order of ,4, to $5 of d mounted in thespace between said electron-optical system and said cathode in closevicinity of said hollow cylindershaped electrode; and means for directlyconnecting said plate-shaped electrode with said anode.

KURT SCHLESINGER.

